Section 3: Functions and features
2606B System SourceMeter® Instrument Reference Manual
3-62
2606B-901-01 Rev. B / May 2018
Source settling times
Each 2606B source-measure unit (SMU) can drive up to 50
µ
F of a capacitance in high-capacitance
mode. To accomplish this, the speed of the 2606B SMU is reduced. Source settling times increase
when high-capacitance mode is enabled. The following table compares examples of the differences in
source settling times between normal and high-capacitance modes.
Source settling times
Range
Normal mode High capacitance mode
100 mV
50
µ
s
200
µ
s
1 V
50
µ
s
200
µ
s
6 V
100
µ
s
200
µ
s
20 V
150
µ
s
7,000
µ
s
In high-capacitance mode, the frequency compensation capacitance across the measure range
resistors increases. This increase leads to longer settling times on some current measure ranges.
The same range elements that are used to measure current are used to source current. Therefore,
the current limit response times will respond in a similar manner. Examples of the differences in
source settling times are shown in the following table.
Current measure and source settling times
Current measure range
Normal mode
(typical)
High capacitance mode (typical)
1 A to 3 A
80
µ
s
120
µ
s (R
load
> 2
Ω)
100 mA
100
µ
s
100
µ
s
10 mA
80
µ
s
100
µ
s
1 mA
100
µ
s
3,000
µ
s
100
µ
A
150
µ
s
3,000
µ
s
10
µ
A
500
µ
s
230,000
µ
s
1
µ
A
2,000
µ
s
230,000
µ
s
When high-capacitance mode is enabled, the amount of time to change the current measure range
increases for each SMU. The current measure range and the current limit range are locked together.
Setting the current limit automatically updates the measure range.
Adjusting the voltage source
When driving large capacitive loads with high-capacitance mode enabled, the response time may be
lengthened by the current limit. For example, see the table titled "Current measure and source settling
times" in the
Understanding source settling times
(on page 3-62) topic. If a 1
µ
F capacitor charges to
10 V in 10
µ
s with a 1 A limit and the limit is set to 100 nA, the charging time will be 100 seconds (see
the following equation).
The total response times while in high-capacitance mode are a combination of the time spent
charging the capacitor (current limit) or the response time, whichever is greater. There is a direct
relationship between the current limit and the charging time. As the current limit decreases, the
amount of time required to charge the capacitor increases.